SCIENCE AS MEASUREMENT 89 



student number two. The clocks recorded minutes 

 and the smaller divisions of time ; great care, however, 

 was required to obtain good results from them. There 

 were four clocks in the observatory, of which the 

 largest had three wheels, one wheel of pure solid brass 

 having twelve hundred teeth and a diameter of two 

 cubits. 



Lest any space on the wall should lie empty a num- 

 ber of paintings were added : Tycho himself in an 

 easy attitude seated at a table and directing from a 

 book the work of his students. Over his head is an 

 automatic celestial globe invented by Tycho and con- 

 structed at his own expense in 1590. Over the globe 

 is a part of Tycho' s library. On either side are repre- 

 sented as hanging small pictures of Tycho's patron, 

 Frederick II of Denmark (d. 1588) and Queen 

 Sophia. Then other instruments and rooms of the 

 observatory are pictured ; Tycho's students, of whom 

 there were always at least six or eight, not to men- 

 tion younger pupils. There appears also his great 

 brass globe six feet in diameter. Then there is pic- 

 tured Tycho's chemical laboratory, on which he has 

 expended much money. Finally comes one of Tycho's 

 hunting dogs very faithful and sagacious ; he serves 

 here as a hieroglyph of his master's nobility as well 

 as of sagacity and fidelity. The expert architect and 

 the two artists who assisted Tycho are delineated in 

 the landscape and even in the setting sun in the top- 

 most part of the painting, and in the decoration 

 above. 



The principal use of this largest quadrant was 

 the determination of the angle of elevation of the 

 stars within the sixth part of a minute, the collinea- 



